A flat flexible cable (FFC) may typically be used as a bridge between motherboard and daughter boards in computing systems including desktops, notebooks, tablets and smartphones. Such cables may be more economical than other cables such as flexible printed circuits and micro-coaxial cables. Absent ground shielding, unshielded FFC cables may have poor impedance match, high insertion loss and high noise radiation. This makes unshielded cables poorly suited for transmitting high speed signals. Universal Serial Bus (USB) 3.0 standard serial ports, for example, may run at speeds in excess of 5 gigabits per second. Equipment manufacturers may instead use more expensive cabling options such as micro-coaxial cables, which increases unit cost.
An FFC cable may have a thin metal sheet attached over a substantial portion of its length to act as an electromagnetic (EM) shield. This improves the cable signal integrity because the wire characteristic impedance may be controlled through the shield. However, if the shield is not properly grounded it is a floating shield, and a floating shield may radiate noise significantly and cause radio frequency interference (RFI) and electromagnetic interference (EMI).